This invention relates generally to methods and apparatus for closing wounds and more particularly, to a method and apparatus for applying optical energy to biological tissue whereby the tissue is converted to a collagenous, denatured protein substance which joins severed tissues and closes wounds.
Historically, suturing has been the accepted technique for rejoining severed tissues and closing wounds. Suturing has been achieved with a surgical needle and suturing thread, and more recently, with a variety of polymeric or metallic staples. The intended function of sutures is to hold the edges of the wounds against one another during healing so as to reduce discomfort, pain, scarring, and the time required for healing.
It is a problem with known suturing systems that since they are applied intermittently along a wound, they permit gaps in the wound between sutures to remain open thereby accepting dirt and bacteria. Moreover, in addition to producing a relatively high risk of infection and tissue rejection, such gaps between sutures are eventually filled in by keloid, which results in disfiguration and scarring. In addition, inflamation often results from the foreign body presence of the suture material.
It is an additional disadvantage of conventional sutures that they may slip in an axial direction thereby permitting relative motion between the tissues which are desired to be joined, and may loosen before the healing process has advanced sufficiently to maintain a tight closure of a wound. Thus, sutures must frequently be removed and replaced, thereby requiring multiple visits to a physician. There is a need, therefore, for a wound closure system which is uniform throughout the length of a wound.
A variety of cauterization and cryogenic techniques have been developed to reduce the flow of blood in an open wound, or a surgically-induced incision. Generally, cauterization is achieved by using intense heat to sear and seal the open ends of the tissues, such as vessels and capillaries. In known cauterization systems, heat is generated by resistance heating of a metallic probe which is subsequently applied to the tissue to be cauterized. Alternatively, undesired blood flow is discontinued by applying a cryogenic temperature which freezes the tissue. More recently, the medical field has utilized high intensity optical energy generated by one or more lasers to achieve cauterization which limits blood flow. In such known laser systems, the optical energy is applied in sufficient quantity to sear or burn the vessels. Laser cauterization is illustratively described in U.S. Pat. No. 4,122,853 to Michael R. Smith. These techniques, however, destroy the surrounding tissue leading to longer healing times, infection, and scarring.
Recent advances in the state of the art have produced cauterization with the use of ultrasonic energy which is converted to mechanical vibrations through a knife. Such a rapidly vibrating knife simultaneously cuts and closes off severed vessels. A system of the ultrasonic vibrational type is described in U.S. Pat. No. 3,794,040 which issued to Balamuth. known system, ultrasonic energy is applied to create heating of the vessels desired to be cauterized above room temperature, but below a temperature at which such vessel would sear. The heat thus produced causes hemeostasis, by denaturing of the proteins in the tissue to form a collagenous substances which performs as a glue to achieve the closure or bond. This technique, however, has not gained widespread use for delicate surgery because it requires bringing a vibrating probe into contact with the tissue to be affected. Moreover, ultrasonic energy is nonpreferentially absorbed and affects all of the surrounding tissue.
Optical energy generated by lasers has been applied in recent times to various medical and surgical purposes because the monochromatic and coherent nature of the light generated by lasers has been shown to have absorbency characteristics which vary with the nature of the illuminated tissue. Thus, for a given tissue type, the laser light may propagate through the tissue, substantially unattenuated, or may be almost entirely absorbed. Of course, the extent to which the tissue is heated, and ultimately destroyed, depends on the extent to which it absorbs the optical energy. It is generally preferred that the laser light be essentially transmissive in tissues which are desired not to be affected, and absorbed by the tissues which are to be affected. For example, when using lasers in fields which are wet with blood or water, it is desired that the optical energy not be absorbed by the water or blood, thereby permitting the laser energy to be directed specifically to the tissues desired to be affected. Such selective absorption also permits substantial time saving during an operation by obviating the need for cleaning and drying the operating field.
It is a further known advantage of a laser system that the optical energy can be delivered to the tissues desired to be operated upon in a precise location and at predeterminable energy levels. The precision with which the laser energy can be directed is enhanced by its ability to be guided by known thin optical fibers which permit the optical energy to be utilized within a body without requiring large incisions or to be inserted into the body through an endoscope. The optical fibers which conduct the laser-generated optical energy for performing the operation can be combined with other optical fibers which conduct light in the visible range, and further optical fibers which are of the image-transmissive type such that a surgeon may view and control an operation which is occurring within a body.
Ruby and argon lasers which are known to emit energy in the visible portion of the electromagnetic spectrum have been used successfully; particularly in the field of ophthalmology to reattach retinas to the underlying choroidea and to treat glaucoma by perforating anterior portions of the eye to relieve intraocular pressure. The ruby laser energy has a wavelength of 0.694 micrometers and, thus, appears red. The argon laser emits energy at 0.488 and 0.515 micrometers, thus, appearing blue-green. The ruby and argon laser beams are minimally absorbed by water, such as tissue water, but are intensely absorbed by the blood chromagen hemoglobin. Thus, the ruby and argon laser energy is poorly absorbed by nonpigmented tissue such as the cornea, lens, and vitreous humor of the eye, but is preferentially absorbed by the pigmented retina where it can then exert a thermal effect.
Another type of laser currently in surgical use is the carbon dioxide (CO.sub.2) gas laser which emits a beam which is intensely absorbed by water. The wavelength of the CO.sub.2 laser is 10.6 micrometers and therefore lies in the invisible, far infrared region of the electro-magnetic spectrum. Reference to FIG. IA shows that the absorption of energy by water in this part of the spectrum is so great that it is absorbed independently of tissue color by all soft tissues having a high water content. Thus, the CO.sub.2 laser makes an excellent surgical scalpel and vaporizer. Since it is so completely absorbed, its depth of penetration is shallow and can be precisely controlled with respect to the surface of the tissue being operated upon. The CO.sub.2 laser is frequently used for neuorological surgery where it is used to vaporize or coagulate neural tissue with minimal thermal damage to underlying tissues.
The fourth commonly used type of laser is the neodymium doped yttrium-aluminum-garnet (Nd:YAG) laser. The Nd:YAG laser has a predominant mode of operation at a wavelength of 1.06 micrometers in the near infrared region of the electromagnetic spectrum. Reference to FIG. IB shows that the Nd:YAG emission at 1 micrometers wavelength is absorbed to a greater extent by blood than by water making it useful for coagulating large bleeding vessels. The Nd:YAG at 1.06 .mu.m laser energy has, for example, been transmitted through endoscopes to treat a variety of gastrointestinal bleeding lesions, such as esophogeal varices, peptic ulcers, and arteriovenous anomolies.